Function Channel.start

Start the setup stage of the channel. Should only be called once.

void start();

A signing task will be spawned which attempts to collect the settlement and trigger transaction signatures from the counterparty. Additionally, the counter-party will request our own settlement & update signatures in the process.

Once the signatures are collected and are validated on our side, the channel will be in WaitingForFunding state and will await for the funding transaction to be externalized before marking the channel as Open.